There is sufficient evidence to show that overexposure to ultraviolet (UV) radiation is the main preventable cause of skin cancers – both melanoma skin cancer (the most serious type) and non- melanoma skin cancers (NMSC).[1,2] The sun is the principal source of natural UV radiation. Sunbeds produce artificial UV radiation.

An estimated 86% of melanomas in the UK (around 11,500 cases) every year are linked to too much exposure to sunlight and sunbed use.[3]

The risk of melanoma is most strongly linked to intermittent sun exposure [4] – short, intense bursts of sun for people who generally spend most of their time indoors, for example sunbathers on holiday.

These people tend to have one or more of the following:
o fair skin[1]
o skin that burns easily[1]
o lots of moles[2] or freckles[1]
o a history of sunburn[3]
o red or fair hair[1]
o light-coloured eyes[1]
o a personal[4,5] or family history of skin cancer.[1,6]

People with naturally dark brown/black skin burn less easily and have a lower risk of skin cancer.[1] But people with darker skin can still develop skin cancers, especially types not related to UV for example on non-pigmented parts of the body like the soles of the feet.[7]

The World Health Organisation (WHO) developed an international UV index to reflect the strength of the sun’s rays (level of UV radiation) at the earth’s surface. There’s a guide to the UV Index available online at: http://www.who.int/uv/publications/en/UVIGuide.pdf . The greater the UV index value, the greater the potential for damage and the less time it takes for this damage to occur.[1,2]

The UV index can be used as an indication for how important it is to protect against UV radiation. It is widely accepted that people are unlikely to be harmed by UV levels below 3.[1,3]

The strength of UV radiation reaching the earth’s surface is affected by several factors including: [2,4,5]
o Time of day, being strongest at solar noon (around 1pm British Summer Time) when the sun is highest in the sky
o Time of year, being strongest in the summer months
o Latitude, being strongest in locations nearer the equator
o Altitude, being higher at higher altitudes
o Cloud cover – over 90% of UV can pass through light cloud
o Reflection – snow can reflect up to 80% of the UV radiation that hits it, increasing a person’s exposure. About 15% of rays are reflected back from sand, 10% from concrete and up to 30% from water (depending on choppiness)

UV radiation from the sun damages the DNA in our skin cells which can lead to the development of cancer.[1] Sunburn is a sign of DNA damage caused by too much UV. There are two main types of UV rays that damage skin and cause skin cancer[1]:
• UVA penetrates deep into the skin. It ages the skin, but contributes much less towards sunburn[2].
• UVB is responsible for the majority of sunburns.

A third type of UV ray, UVC, could be the most dangerous of all, but it is completely blocked out by the ozone layer and doesn’t reach the earth's surface.[1]

Getting a sunburn just once every two years can triple the risk of melanoma.[3]

Sunburn during childhood or adolescence can increase the risk of skin cancer later on in life. But sunburn at any age increases the risk of malignant melanoma. [3,4]

It is widely agreed that a combination of measures including using shade and clothing as the first lines of defence and sunscreen for the parts you can’t cover, offers the best protection against over-exposure to UV radiation from the sun.[1,2] Research suggests that shade and clothing offer better protection from UV rays than sunscreen. [3–6]

Shade
Shade structures can provide protection from the sun. Staying under shade, such as a tree or umbrella, can reduce your overall exposure to UV, but not completely protect you.[7] Many shade structures are more likely to filter than to block UV radiation. Only very broad and thick shade such as thickly wooded areas and widely overhanging structures provide enough protection from strong sun.[8]

Clothes, hats, sunglasses
Covering up with clothes, hats and sunglasses is an effective way of protecting yourself from UV rays.[2]

Clothes tend to provide more protection if they:[1,2,9–12]
o Cover more skin – e.g. long-sleeved t-shirts and wide brim hats
o Are loose fitting
o Are deeper colours
o Are made of polyester preferably, or wool, silk or nylon. Cotton, rayon, linen and viscose fabrics tend to be less protective
o Are dry – for example cotton is less protective when wet
o Are thicker
o Have a close weave– check you can’t see through the fabric.

Wide-brimmed hats provide the most UV protection for the whole face and head.[1,2] Caps protect the nose and forehead but provide poor protection for other parts of the face.

Sunglasses can protect your eyes from too much UV exposure. Poorly-fitting sunglasses offer poor protection as sunlight can reflect off the back face of the lens back into the eye. Wraparounds are recommended.[2] Because of the angle of the sun, eyes can be at risk of damage and need protection earlier in the morning and later in the afternoon than for the rest of your body.[13]

Sunglasses should state that they block out 100% of UVA and UVB rays. Alternatively, look for the ‘CE Mark’ and British Standard, or a UV 400 label.

Sunscreen
Many studies have shown that sunscreen can reflect or absorb harmful UV rays.[14] However, whether or not using sunscreen reduces skin cancer risk remains unclear.[15–18] How sunscreen is applied and how using it affects someone’s subsequent behaviour, consciously or unconsciously, are important considerations.[19]

Using sunscreen for ‘non-intentional’ sun exposure, where the aim of the activity isn’t to expose skin to the sun but it may happen incidentally, such as walking, gardening, sport or other daily activities, may reduce the risk of sunburn.[20] However, using sunscreen for ‘intentional’ sun exposure (e.g. sunbathing) has been linked with people spending longer in the sun overall and being no less likely, perhaps even more likely to get sunburnt.[21] This was particularly seen when people used higher SPF sunscreens.

Because of this, we recommend that sunscreen should be used together with clothing and shade to protect the skin from sun damage, and should never be used to spend longer in the sun.

The SPF or ‘factor’ of a sunscreen is a measure of the amount of sun protection it provides. Experts have found that SPF 15 sunscreen provides sufficient protection when used appropriately, wherever you are in the world.[14,22] One study has found benefit for reduction in skin cancer risk for sunscreens of SPF15 or above, compared to below SPF 15.[18] A minimum of SPF 15 is recommended by NICE (National Institute for Health and Care Excellence).[2] No sunscreen is 100% effective and as SPF increases, sunscreens provide less and less extra protection.[19]

SPF measurements are based on the assumption that people apply 2mg/cm2 of sunscreen on their body.[14] But research has shown that people don’t apply enough. Studies have found the actual amount applied is less than half of the level SPF is tested at (0.39 to 1.0 m/cm2).[23]

Sunscreen only works if you use enough. It should be applied evenly, thickly and regularly to be effective.[2] As a guide, for an average adult, you should use:[2]
o around two teaspoonfuls of sunscreen if you're just covering your head, arms and neck.
o around two and a half tablespoonfuls if you're covering your entire body, for example while wearing a swimming costume.

Sunscreens that provide UVA protection are recommended.[2] The star rating system measures the balance between UVA and UVB protection and awards products a rating of 1-5 stars. It is not an absolute measure, but depends on the SPF rating of the sunscreen it is applied to. Sunscreen with at least 4 stars is recommended.[2]

The International Agency for Cancer Research (IARC) state there is sufficient evidence that sunbed use causes melanoma, and limited evidence that sunbed use causes squamous cell carcinoma (a type of non-melanoma skin cancer).[1,2]

Combining the results of studies on sunbeds and cancer shows that using a sunbed at any age increases melanoma risk by 16-20%.[3,4]

Sunbeds are no safer than exposure to the sun itself.[1] One study found that the average skin cancer risk from sunbeds can be more than double that of spending the same length of time in the Mediterranean midday summer sun.[5]

Far from being a sign of health, a tan is a reaction to DNA damage in the skin.[1] It is a sign that your body is trying to repair damage that has already happened.[2]

Some people think a pre-holiday tan or sunbed tan will protect them from burning but a tan offers very little protection against the sun.[3] Some studies have found that tans only offer protection equivalent to using SPF 3 sunscreen – nowhere near the minimum recommended SPF15 - and tans from sunbeds that mostly produce UVA radiation could be as low as SPF 1.[4]

“Fake tan” lotions, sprays, creams and mousses are products applied to the skin that contain the active ingredient dihydroxyacetone (DHA). DHA is a chemical which reacts with the protein in the top layer of skin, to form brown-black compounds called melanoidins.[1]

Our bodies produce vitamin D when our skin is exposed to UV rays from the sun. This is the main source of this vitamin.[1] We all need vitamin D to help build and maintain strong bones. If you are severely lacking in vitamin D this may lead to rickets in children and a condition called osteomalacia in adults.[1]

In summer, most white people in the UK only need to spend a short amount of time in the sun unprotected to make enough vitamin D.[1–3] This is typically less than the time taken to lead to sunburn.[3] People with darker skin tones might need longer in the sun, but also have a lower risk of sunburn and skin cancer.[3,4] It should be possible for most people to find a balance between enjoying the beneficial effects of the sun while not increasing the risk of skin cancer.

Vitamin D synthesis is much lower in winter months in countries at higher latitudes like the UK because the UV isn’t as strong.[5] In summer some vitamin D may be stored to help maintain levels across the year.[1,2,6]

The Government recommends that people at risk of vitamin D deficiency should take vitamin D supplements throughout the year. Between October and the end of March they also recommend people in the UK consider taking a daily vitamin D supplement. You can find out more here: http://www.nhs.uk/Conditions/vitamins-minerals/Pages/Vitamin-D.aspx

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